1. Field of the Invention
The present invention relates to an electroosmotic movable device using induced-charge electro-osmosis, and more concretely relates to an electroosmotic movable device applicable to an actuator, a fluid valve, an optical scanner and the like.
2. Description of the Related Art
Micro-pumps using electro-osmosis are relatively simple in structure. They are used in the field of μTAS (Micro-Total Analysis System) and the like for the reason of being relatively simple in structure and being easily mounted into micro-channels.
Among them, micro-pumps using induced-charge electro-osmosis (ICEO: Induced-Charge Electro-osmosis) have attracted attention in recent years. The reasons of this include the fact that the micro-pumps can increase the flow velocity of liquids and can suppress chemical reactions occurring between the electrodes and the liquids by being capable of AC drive.
U.S. Pat. No. 7,081,189 and M. Z. Bazant and T. M. Squires, Phys. Rev. Lett. 92, 066101 (2004) disclose pumps using induced-charge electro-osmosis and having the following (1) and (2).
Specifically, (1) a pump (half coat type ICEO pump) which controls the flow of a liquid in such a manner that a coating of a dielectric thin film is applied to half of a metal post placed between electrodes to control the region of the electric charges induced in the metal post by an electric field applied. (2) A pump (asymmetrical metal post shape type ICEO pump) which controls the flow of a liquid in a constant direction by disposing a metal post in asymmetrical shape such as a triangle between electrodes.
K. A. Rose et al., Phys. Rev. E75, 011503 (2007) discloses rotation of a micro-rod using ICEP (Induced-Charge Electrophoresis).
Further, S. Gangwal, O. J. Cayre, M. Z. Bazant, and O. D. Velev, Phys. Rev. Lett. 100 058302 (2008) discloses the electrophoresis phenomenon of metal particles with an insulating coat applied to a half of the metal particles.
Meanwhile, a number of compact actuators (electrostatic actuators) using electrostatic force in the air are disclosed.
However, when an electrostatic actuator which is devised to be mainly used in the air is placed in an electrolytic solution such as water, the electric field is shielded by ions in the electrolytic solution, and therefore, the problem arises that the electrostatic force does not work. Thus, realization of a compact actuator has been difficult.
Further, in the art of moving a movable part in a solution by using external force such as magnetic force, not only reduction in size of the drive part has been difficult, but also drive of the movable part at a high velocity has been difficult due to frictional force or viscous resistance (flow resistance) which occurs on the interface of the solid and liquid due to the viscosity of the liquid.
Further, the arts described in U.S. Pat. No. 7,081,189, M. Z. Bazant and T. M. Squires, Phys. Rev. Lett. 92, 066101 (2004), K. A. Rose et al., Phys. Rev. E75, 011503 (2007) and S. Gangwal, O. J. Cayre, M. Z. Bazant, and O. D. Velev, Phys. Rev. Lett. 100 058302 (2008) do not suggest or disclose a so-called actuator technique that drives a movable body having a rotating shaft or a supporting point.
The present invention is made in view of such a background art, and provides an electroosmotic movable device which uses induced-charge electro-osmosis and can be used as an actuator or the like in a liquid, particularly in an electrolytic solution.